Downhole Jet Pump

ABSTRACT

A downhole jet pump  10  includes an exterior pump housing  12,  the jet nozzle  30,  and a carrier  40.  A diffuser  46  is provided downstream from a mixing tube  32,  and preferably forms a unitary body sealed to the pump housing. An inlet valve  100  passes formation fluid to the pump housing.

FIELD OF THE INVENTION

The present invention relates to jet pumps and, more particularly, tojet pumps commonly used downhole in wells to pump formation fluids orother fluids to the surface. The downhole jet pump as disclosed hereinhas a comparatively high efficiency and may be operated in either thedirect flow or reverse flow modes.

BACKGROUND OF THE INVENTION

Jet pumps have long been used for recovering hydrocarbons from downholeformations. The potential for jet pumps is enhanced by its relativelylow cost compared to artificial lift systems that use reciprocating onrotating rod strings to pump fluids to the surface.

Various problems have limited the success of jet pumps in thehydrocarbon recovery industry. Jet pumps may be operated in a directflow mode, where the driving fluid is pumped down the tubing string andto the jet pump, and fluid is pumped by the jet pump to the surface inan annulus between the tubing string and the casing. Alternatively, jetpumps may be operating in the reverse flow mode, wherein the drivingfluid is pumped down the annulus to the jet pump, and the formationfluid and driving fluid are pumped to the surface through the tubingstring. While direct pump flow is more common than reverse pump flow,the ability to pump in either direction is desired by many operators,and the costs of the jet pumps for accomplishing these goals isunfortunately increased by the large number of different partsconventionally used to maintain both direct flow jet pumps and reverseflow jet pumps.

Other problems with jet pumps relate to their relatively low efficiencycompared to other artificial lift systems for returning hydrocarbons tothe surface, the additional costs associated with retrieving pressure ortemperature sensors to the surface after the jet pump is retrieved, andtechniques which allow adjustment of the axial spacing between thenozzle and the mixing tube which receives fluid from the nozzle.

Prior art patents directed to jet pumps include U.S. Pat. Nos.4,858,893, 5,083,609, 5,055,022, and 7,909,089. Another jet pump isdisclosed in a Volcanica website underwww.youtube.com/watch?v=nDYFpBUBwic. Some of these patents discussreverse flow to pump a component to the surface, but the pump is notoperating as a jet pump during this component retrieval operation.

The disadvantages of the prior art are overcome by the presentinvention, and an improved downhole jet pump is hereinafter disclosed.

SUMMARY OF THE INVENTION

In one embodiment, a downhole jet pump is provided for positioning in awell on a tubular string to pump formation fluids from the well. The jetpump includes an exterior pump housing defining an elongate passagewaytherein. A jet nozzle has an exterior sealed to the pump housing andincreases the fluid velocity of the power fluid transmitted downhole tothe jet nozzle. A mixing tube positioned downstream from the jet nozzlehas an elongate mixing tube passageway for receiving fluid from the jetnozzle and fluid from the formation. In one embodiment, a diffuser isprovided downstream from the jet nozzle and has a lower end passingthrough a side port in the pump housing.

These and further features and advantages of the present invention willbecome apparent from the following detailed description, whereinreference is made to the figures in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of one embodiment of a downhole jetpump according to the present invention.

FIG. 2 is a cross-sectional view of a downhole jet pump similar to thatshown in FIG. 1, with the nozzle and mixing tube reversed for flow tothe surface through a tubing string.

FIG. 3 is a detailed view of pump components configured for a reverseflow.

FIG. 4 is a detailed view of pump components configured for direct flow.

FIG. 5 illustrates temperature and/or pressure probe connected to thejet pump, with a standing valve positioned below the probe.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 depicts one embodiment of a downhole jet pump 10 for positioningwithin a well from a tubular string to pump formation fluid from thewell to an annulus surrounding, the tubing string, and then from thatannulus up to the surface. Those skilled in the art will appreciate thata downhole jet pump may be used for pumping liquid hydrocarbons from awell, but may also be used for pumping other fluids, such as water, toenhance the production of gas or other valuable fluids. The jet pump isadapted for receiving power fluid from a tubular, and pumping both thepower fluid and the formation fluid to the surface. Various functionalcomponents of a jet pump may alternatively be arranged for reverse flow,as explained subsequently, so that the power fluid is transmitted downthe annulus and the formation fluid and power fluid are recovered at thesurface through the tubing string.

The jet pump 10 includes an exterior pump housing 12 which defines anelongate housing passageway 14 therein extending from an upper portionto a lower portion of the pump housing. The exterior pump housing 12preferably has a generally outer cylindrical surface 16 and a generallycylindrical inner surface 18 which defines the passageway in the pumphousing. Ported sub 62 surrounds pump housing 12, and is threaded toupper seal sub 60, which is threaded to the tubing string. The pumphousing is thus generally tube or sleeve shaped, with its ends securedto both a top pin 20 and a bottom pin 24, respectively. The top pin 20is adapted for sealing engagement with the tubular string. A lower sealsub 22 may be provided at the lower end of the pin 24, and is threadedto tubular 62. Pin 24 has a passageway 28 providing an inlet forhydrocarbons into the pump housing when pumping in the direct flow mode.

FIG. 1 depicts a power fluid jet nozzle 30 with a passageway 31 whichbecomes axially restrictive in the downward direction, therebyincreasing the velocity of power fluid transmitted through the jetnozzle. The jet nozzle 30 is supported on and has an exterior sealed tothe carrier 40, which includes circumferentially spaced ports 41. Amixing tube 32 within carrier 40 is provided fluidly downstream from thejet nozzle, and has an elongate mixing tube passageway 34 receivingpower fluid from the jet nozzle 30. A plurality of venturi ports 41 oran axial spacing 38 between the lower end of the nozzle and an upper endof the mixing tube provided immediately below the nozzle 30 allow forentry of formation fluids from within the housing 12 and into the mixingtube 32. The mixing tube 32 preferably may be formed from a tungstencarbide alloy material to define the mixing tube passageway 34.

The pump as shown in FIG. 1 also includes a diffuser 46. The lowerportion 50 of the diffuser includes a substantially circular curved bore56. Diffuser 46 has a significant advantage over a cross-over sub, whichis used in other jet pumps. A cross-over sub typically has a pluralityof relatively small diameter flow paths to pass formation fluid to thejet nozzle, while the diffuser provides a relatively largecircumferential flow path 14 between the pump housing and both thediffuser and the mixing tube. An inlet or standing valve 100 as shown inFIG. 5 is provided at the lower end of the pump housing, and isretrievable by a wire line.

The jet pump 10 as shown in FIG. 1 is thus configured for direct fluidflow, wherein fluid is pumped down the tubing string and passes throughthe top pin 20 to the nozzle 30, which increases fluid velocity for thefluid exiting the nozzle 30 and drawing fluid from the annulus 14, thusdrawing in formation fluid so that both the drive fluid and theformation fluid pass through the mixing tube 32 and exit the pumpthrough the outlet from the diffuser 46 and into the annulus between thepump housing 12 and the outer housing 62. Formation fluid thus entersinterior the housing through the flow path provided in the pin 24 andpasses upward in the annulus 14 to the surface. Fluid discharged by thepump thus passes upward in the well in the annulus between the casingand the tubing string.

FIG. 4 shows in greater detail the nozzle 30 and mixing tube 32. Sub 76may be threadably connected to carrier 40, so that nozzle 30 issandwiched between the lower end of sub 76 and shoulder 75 on thecarrier. Carrier 40 includes the circumferentially spaced ports 41discussed above. The upper end of sleeve 76 includes conventional seals72 for sealing with the top sub 60. Lower sub 78 is also threaded tocarrier 40, and includes O-ring seals 76 for sealing with the diffuser46.

FIG. 3 discloses the same nozzle 30 and mixing tube 32. Sub 76 has beenreplaced with sub 70, which contains O-rings 72. Sub 78 is replaced withsub 74, and has similar O-rings as 76. The carrier 40 containing thenozzle 30 and the mixing tube 32 is thus inverted in FIG. 3 compared toFIG. 4 for reverse fluid flow.

Referring to FIGS. 3 and 4, the term “carrier” as used herein includesnot only the tube 40 which surrounds the jet nozzle 30 and the mixingtube 32, but also includes the subs 70, 74, 77 and 78 each secured tothe tube 40 and retrievable with the tube 40. These subs, which mayfunctionally be considered part of the carrier, include O ring seals 72,76 for sealing the carrier to either of the outer subs 60, 22, and areretrieved with the tube 40. The sealing diameter of the subs 70, 76, 77,and 78 are thus substantially the same, so that the carrier with thesubs can be inverted from a direct fluid flow configuration as shown inFIG. 4 to the reverse fluid flow configuration as shown in FIG. 3, whilestill maintaining sealing engagement between the carrier and the outersubs 60, 22.

FIG. 2 illustrates the pump as shown in FIG. 1 with the jet nozzle andmixing tube inverted from the FIG. 1 embodiment. Except for theinversion of jet nozzle 30 and mixing tube 32 from the FIG. 1embodiment, the primary components of the pump as shown in FIG. 2 aresubstantially identical to the components shown in FIG. 1. Since thejetting force is down for the direct flow FIG. 1 configuration, noadditional components are required to maintain the jet nozzle and mixingtube in the position as shown in FIG. 1. For the FIG. 2 configurationfor reverse flow, the jetting force is upward, and accordingly the upperend of the FIG. 2 embodiment has components which retain the jet nozzleand mixing tube as shown in FIG. 2, and do not allow these components tobe pumped upward and instead secure the components in place. Moreparticularly, FIG. 2 shows an upper housing 102 which is adapted forengagement with a tubular string (not shown). Sleeve 100 is positionedradially within housing 102. Leaf spring 108 or other biasing means biasthe dogs 104 into engagement with the annular pocket 106, therebyretaining the assembly in place. If it is desired to retrieve the innercomponents in the FIG. 2 embodiment, a conventional tool may be used tounlatch the dogs 104, so that the sub-assembly including components 102,110, 108 and 104 may be retrieved to a surface while the seal sub 60 andported sub 62 remain in place.

FIG. 5 illustrates a lower end of the pump disclosed above, wherein thepump housing 12 includes sleeve 82, which is sealed to the housing 62.Coupling 86 connects housing 62 with tubular 88 extending down fromcoupling 86. The temperature and/or pressure probe 90 is supported onbase 92, and is supported on the tubular 84. When the jet pump isretrieved to the surface, probe 90 is also retrieved with the pump, so aseparate operation to retrieve the probe is not required. If desired,the standing valve 100 as shown in the bottom of FIG. 5 may subsequentlybe retrieved by a wire line operation. As previously stated, the pumpand the probe may be returned to the surface without pulling the tubularstring, so that a work over rig is not required.

In both the direct flow configuration as shown in FIG. 4 and the reverseflow configuration as shown in FIG. 3, seals 72, 76 allow for a limitedaxial movement of the carrier with the nozzle and the mixing tube, whilemaintaining sealed engagement with the pump housing. Also, the axiallength of a sleeve-shaped insert 94 as shown in FIGS. 3 and 4 may beused to selectively control the axial spacing between the tip of thenozzle 30 and the entrance to the mixing tube 32. The sleeve-shapedinsert 94 thus serves as an adjustment mechanism for adjusting the axialspace between the jet nozzle and the mixing tube.

Comparing FIGS. 3 and 4, the carrier tube which houses the jet nozzleand the mixing tube may be reversed end to end when switching from adirect pump mode to a reverse pump mode, or vise versa. Additional endcouplings may be manufactured, and may be the only components one needsto use the direct pump configuration or the reverse flow pumpconfiguration.

The jet pump as disclosed herein is well suited for a frac flowbackoperation, when the jet pump is used to reduce formation pressurerequired to recover the fluid, including freeing fluids to the surface.Although the jet pump may frequently be operated in the direct flowmode, the easy switch to reverse flow mode may be particularlybeneficial for certain applications, including the reliable return offormation sand with the recovered fluid to the surface, and sour gasoperations wherein the recovered fluid does not contact the casing.Also, substantially the same pump components may be used for either thedirect flow or the reverse flow applications, so that a large inventoryof direct flow jet pump components and another inventory of reverse flowjet pump components are not required.

The entire jet pump as disclosed herein is retrievable to the surfacewithout pulling the tubing string, which may remain in the well duringretrieval and reinsertion of a jet pump. Recovery of the jet pump thusneed not entail the substantial expense and time of the workover rig topull the tubing string with the jet pump.

Although specific embodiments of the invention have been describedherein in some detail, this has been done solely for the purposes ofexplaining the various aspects of the invention, and is not intended tolimit the scope of the invention as defined in the claims which follow.Those skilled in the art will understand that the embodiment shown anddescribed is exemplary, and various other substitutions, alterations andmodifications, including but not limited to those design alternativesspecifically discussed herein, may be made in the practice of theinvention without departing from its scope.

What is claimed is:
 1. A downhole jet pump for positioning in a well ona tubular string to pump fluids from the well to the surface,comprising: an exterior pump housing defining an elongate housingpassageway therein having a central axis and extending from an upperportion to a lower portion of the pump housing; a power fluid jet nozzlehaving an exterior sealed to the pump housing, the jet nozzle having ajet passageway therein for increasing fluid velocity of power fluidtransmitted through the jet nozzle; a mixing tube fluidly downstreamfrom the jet nozzle and having an elongate mixing tube passagewayreceiving fluid from the jet nozzle; a diffuser fluidly downstream fromthe mixing tube and having a curved flow path therein, the diffusersealed to the exterior pump housing and the flow path in the diffuserbeing in communication with a throughport in the pump housing, acircumferential spacing between an exterior surface of the diffuser andan interior surface of the pump housing defining a flow path forformation fluid flowing to the jet nozzle; and a carrier in the pumphousing and supporting the jet nozzle and the mixing tube, the carrierincluding one or more ports for passing formation fluid radially inwardto the jet nozzle, the carrier having a first end for sealing witheither the pump housing and the diffuser, and an axially opposing secondend for sealing with the other of the pump housing and the diffuser,such that the carrier, the jet nozzle, and the mixing tube may bearranged for direct flow or may be inverted in the pump housing forreverse flow.
 2. The jet pump as defined in claim 1, further comprising:an adjustment mechanism for adjusting an axial position between the jetnozzle with respect to the mixing tube.
 3. The jet pump as defined inclaim 1, wherein the adjustment mechanism is a selected axial lengthsleeve supporting the jet nozzle.
 4. The jet pump as defined in claim 1,further comprising: a temperature and/or pressure probe supported in thewell from the jet pump housing, such that retrieval of the jet pumphousing to the surface retrieves the probe.
 5. The jet pump as definedin claim 1, wherein the carrier is sealed to the pump housing and to thediffuser, such that there is limited axial movement of the carrier withrespect to the pump housing and the diffuser.
 6. The jet pump as definedin claim 1, further comprising: an inlet valve below the pump housingfor controlling formation fluid flow to the pump housing.
 7. A downholejet pump for positioning in a well on a tubular string to pump fluidsfrom the well to the surface, comprising: an exterior pump housingdefining an elongate housing passageway therein having a central axisand extending from an upper portion to a lower portion of the pumphousing; a power fluid jet nozzle having an exterior sealed to the pumphousing, the jet nozzle having a jet passageway therein for increasingfluid velocity of power fluid transmitted through the jet nozzle; amixing tube fluidly downstream from the jet nozzle and having anelongate mixing tube passageway receiving fluid from the jet nozzle; adiffuser fluidly downstream from the mixing tube and having a curvedflow path therein, the diffuser sealed to the exterior pump housing andthe flow path in the diffuser being in communication with a throughportin the pump housing, a circumferential spacing between an exteriorsurface of the diffuser and an interior surface of the pump housingdefining a flow path for formation fluid flowing to the jet nozzle; anda carrier in the pump housing radially exterior of both the jet nozzleand the mixing tube and supporting the jet nozzle and the mixing tube,the carrier including an opening for passing formation fluid radiallyinward to the jet nozzle, the carrier having axially opposing ends eachfor sealing with either the pump housing or the diffuser, such that thecarrier, the jet nozzle, and the mixing tube may be arranged for directflow or may be inverted in the pump housing for reverse flow.
 8. The jetpump as defined in claim 7, further comprising: an adjustment mechanismfor adjusting an axial position between the jet nozzle with respect tothe mixing tube.
 9. The jet pump as defined in claim 8, wherein theadjustment mechanism is a selected axial length sleeve supporting thejet nozzle.
 10. The jet pump as defined in claim 7, further comprising:a temperature and/or pressure probe supported in the well from the jetpump housing, such that retrieval of the jet pump housing to the surfaceretrieves the probe.
 11. The jet pump as defined in claim 7, furthercomprising: an inlet valve below the pump housing for controllingformation fluid flow within the pump housing.
 12. A method of operatinga downhole jet pump positioned in a well on a tubular string to pumpfluids from the well to the surface, comprising: providing an exteriorpump housing defining an elongate housing passageway therein having acentral axis and extending from an upper portion to a lower portion ofthe pump housing; positioning a power fluid jet nozzle having anexterior sealed to the pump housing, the jet nozzle having a jetpassageway therein for increasing fluid velocity of power fluidtransmitted through the jet nozzle; positioning a mixing tube fluidlydownstream from the jet nozzle and having an elongate mixing tubepassageway receiving fluid from the jet nozzle; providing a diffuserfluidly downstream from the mixing tube and having a curved flow paththerein, the diffuser sealed to the exterior pump housing and the flowpath in the diffuser being in communication with a throughport in thepump housing, a circumferential spacing between an exterior surface ofthe diffuser and an interior surface of the pump housing defining a flowpath for formation fluid flowing to the jet nozzle; providing a carrierin the pump housing and supporting the jet nozzle and the mixing tube,the carrier including ports for passing formation fluid radially inwardto the jet nozzle, the carrier having axially opposing ends each forsealing with either the pump housing and the diffuser, such that thecarrier, the jet nozzle, and the mixing tube may be arranged for directflow; and inverting the carrier, the jet nozzle and the mixing tube inthe pump housing for reverse flow.
 13. The method as defined in claim12, further comprising: adjusting an axial position between the jetnozzle with respect to the mixing tube.
 14. The method as defined inclaim 12, further comprising: supporting a temperature and/or pressureprobe in the well from the jet pump housing, such that retrieval of thejet pump housing to the surface retrieves the probe.
 15. The method asdefined in claim 12, wherein the carrier is sealed to the pump housingand to the diffuser, such that there is limited axial movement of thecarrier with respect to the pump housing and the diffuser.
 16. Themethod as defined in claim 12, further comprising: positioning an inletvalve below the pump housing for controlling formation fluid flow withinthe pump housing.